The holothurian (Echinodermata) diversity of the Glorieuses Islands (Eparses Islands, France, Mozambique channel)

Abstract

Glorieuses archipelago is one of the Eparses Islands, French islands scattered in the Mozambique Channel (Western Indian Ocean). These isolated coral islands, without permanent human population, are important to evaluate the evolution of biodiversity without direct anthropogenic influence. Among several aims, the program BioReCIE (Biodiversity, Resources and Conservation of Eparses Islands) was to complete the inventories of several groups including the holothurians (Echinodermata). In November 2012, a multidisciplinary team explored the reef slopes of the island by scuba diving down to 20 meters (10 sites), and the reef flats at low tide (12 sites) collecting specimens and taking photos for identification. The total holothurian richness was 20 species; 10 species were collected on the slopes and 15 on the reef flats. Given the limited number of sites studied, the occurrence of the different species in each class is presented as frequent, infrequent or rare. The commercial species Holothuria nobilis, Bohadschia atra and B. subrubra were frequent but illegal fisheries on holothurians are already occurring. Temporal comparisons at local and regional scales using the same methodology show that the diversity in Glorieuses is high and suggests that the biodiversity is increasing as we go from South to North in the Mozambique channel, as observed also for other taxa associated with coral reefs (fish and hard corals).